Toner attached to an image (electrostatic latent image) formed on a photosensitive element to develop the image is electrostatically transferred to a transfer material such as paper by a transfer step. However, about several to 20% of the toner attached to the photosensitive element remains on the photosensitive element without being completely be transferred. If the residual toner on the outer surface of the photosensitive element is carried to the next developing step, a charging device cannot sufficiently charge the photosensitive element since a portion of the outer surface of the photosensitive element where the toner remains is blocked by the toner. Accordingly, an image formed next becomes defective. Besides the toner, if paper powder or the like is carried to the next developing step without being cleaned, it may enter the developing device in a developing area to cause an imaging failure, a developing device trouble or other problem.
Accordingly, in conventional image forming apparatuses, a cleaning device is provided to remove the toner and other materials residual on the photosensitive element. A variety of cleaning methods including magnetic brush-cleaning, electrostatic brush-cleaning, brush-cleaning, magnetic roller-cleaning, blade-cleaning have been proposed as cleaning methods. Among these methods, the brush-cleaning and blade-cleaning are generally used in combination since they provide a satisfactory cleaning performance.
However, the use of the brush-cleaning and blade-cleaning in combination causes an image degradation since the outer surface of the photosensitive element is scraped by a cleaning blade held in strong sliding contact with the outer surface of the photosensitive element. Further, a frictional heat is produced in a position where the cleaning blade is in contact with the photosensitive element and fuses the residual toner to adhere to the outer surface of the photosensitive element, thereby causing so-called "black dots" in a final image.
In view of the above problem, an object of the present invention is to provide a cleaning device which suppresses the adhesion of toner to the outer surface of the photosensitive element by fusion and the scraping of the photosensitive element while maintaining a satisfactory cleaning performance.